Killer cold: Winter is deadlier than summer in U.S.

Diego Ramos, who is homeless and lives under nearby building scaffolding, pauses as he clears a sidewalk following a storm that left up to eight inches of snow in New York City.(Photo: Spencer Platt, Getty Images)

Winter cold kills more than twice as many Americans as does summer heat, according to a report released today by the National Center for Health Statistics (NCHS), a division of the Centers for Disease Control and Prevention.

Based on death certificate data from 2006-10, the report's authors found that "about 2,000 U.S. residents died each year from weather-related causes of death." The CDC report found that 63% of these deaths were attributed to exposure to excessive natural cold, hypothermia or both, while about 31% of these deaths were attributed to exposure to excessive natural heat, heat stroke, sun stroke or all.

Only about 6% were attributed to floods, severe storms, tornadoes, hurricanes or lightning.

"This is the first report from the National Center for Health Statistics to focus on weather-related death by place of residence," said report co-author Jennifer Parker, chief of the special projects branch at the NCHS. The authors studied the causes of death on death certificates as prepared by coroners or medical examiners. Deaths when weather was an underlying or contributing cause were included.

One interesting finding, according to Parker, was the high number of deaths in the rural West due to the cold. Not surprisingly, most of the heat-related deaths occurred in the warmer South and West. The report also found that the rate of heat-related mortality was higher in the most urbanized — along with the most rural — counties.

Most weather deaths in this study were "quieter" deaths, said report lead author Deborah Ingram of the NCHS. They don't get the attention of the catastrophic storm events such as tornadoes and hurricanes, which are very visible, dramatic events that cause some deaths and sometimes widespread economic destruction.

This report also found that older people, men and non-Hispanic blacks had higher weather-related death rates than other ages, women, and other race and ethnicity subgroups.

Additionally, the combined effects of a warming climate, the aging U.S. population and the increasing number of people living in urban areas (where the urban heat island effect exacerbates the effects of high temperatures) may result in an increasing number of people at risk of heat-related death.

The CDC death data differ from data produced by the National Weather Service (NWS), which finds that, based on a 10-year average from 2004-13, only about 640 people die because of weather each year. Weather service data find that heat is the biggest killer, followed by tornadoes, hurricanes and floods. Cold is only the eighth-biggest killer, the NWS reports.

Why the discrepancy? "The NWS' fatality and injury information is derived from a database where the primary function is to collect weather reports and any details associated with an event's impact," said Brent MacAloney, NWS Storm Data Program Manager. "The fatality and injury information is only supplementary."

"In the case of the heat fatalities and injuries, only those fatalities that occurred when atmospheric conditions met the local weather service forecast office's advisory or warning conditions would be documented. The same logic is used for the cold fatalities and injuries," he said.

The CDC death data almost always include weather conditions, regardless of whether it was severe or unusual or met the weather service's advisory and warning criteria.

For instance, in the CDC study, "the heat-related deaths were not necessarily during a heat wave," Parker said.

However, neither set of statistics included weather-related traffic accidents, which kill more than 7,000 Americans each year on our nation's highways, according to data from the Federal Highway Administration.